Carnes Cynthia A, Janssen Paul M L, Ruehr Mary L, Nakayama Hitomi, Nakayama Tomohiro, Haase Hannelore, Bauer John Anthony, Chung Mina K, Fearon Ian M, Gillinov A Marc, Hamlin Robert L, Van Wagoner David R
College of Pharmacy, Ohio State University, Columbus, Ohio 43210, USA.
J Biol Chem. 2007 Sep 21;282(38):28063-73. doi: 10.1074/jbc.M704893200. Epub 2007 Jul 25.
Atrial fibrillation (AF) is characterized by decreased L-type calcium current (I(Ca,L)) in atrial myocytes and decreased atrial contractility. Oxidant stress and redox modulation of calcium channels are implicated in these pathologic changes. We evaluated the relationship between glutathione content (the primary cellular reducing moiety) and I(Ca,L) in atrial specimens from AF patients undergoing cardiac surgery. Left atrial glutathione content was significantly lower in patients with either paroxysmal or persistent AF relative to control patients with no history of AF. Incubation of atrial myocytes from AF patients (but not controls) with the glutathione precursor N-acetylcysteine caused a marked increase in I(Ca,L). To test the hypothesis that glutathione levels were mechanistically linked with the reduction in I(Ca,L), dogs were treated for 48 h with buthionine sulfoximine, an inhibitor of glutathione synthesis. Buthionine sulfoximine treatment resulted in a 24% reduction in canine atrial glutathione content, a reduction in atrial contractility, and an attenuation of I(Ca,L) in the canine atrial myocytes. Incubation of these myocytes with exogenous glutathione also restored I(Ca,L) to normal or greater than normal levels. To probe the mechanism linking decreased glutathione levels to down-regulation of I(Ca), the biotin switch technique was used to evaluate S-nitrosylation of calcium channels. S-Nitrosylation was apparent in left atrial tissues from AF patients; the extent of S-nitrosylation was inversely related to tissue glutathione content. S-Nitrosylation was also detectable in HEK cells expressing recombinant human cardiac calcium channel subunits following exposure to nitrosoglutathione. S-Nitrosylation may contribute to the glutathione-sensitive attenuation of I(Ca,L) observed in AF.
心房颤动（AF）的特征是心房肌细胞中的L型钙电流（I(Ca,L)）降低以及心房收缩力减弱。氧化应激和钙通道的氧化还原调节与这些病理变化有关。我们评估了接受心脏手术的AF患者心房标本中谷胱甘肽含量（主要的细胞还原部分）与I(Ca,L)之间的关系。与无AF病史的对照患者相比，阵发性或持续性AF患者的左心房谷胱甘肽含量显著降低。用谷胱甘肽前体N-乙酰半胱氨酸孵育AF患者（而非对照患者）的心房肌细胞会导致I(Ca,L)显著增加。为了检验谷胱甘肽水平与I(Ca,L)降低在机制上相关的假设，用谷胱甘肽合成抑制剂丁硫氨酸亚砜胺对犬进行48小时治疗。丁硫氨酸亚砜胺治疗导致犬心房谷胱甘肽含量降低24%，心房收缩力降低，以及犬心房肌细胞中I(Ca,L)减弱。用外源性谷胱甘肽孵育这些肌细胞也可使I(Ca,L)恢复到正常或高于正常水平。为了探究谷胱甘肽水平降低与I(Ca)下调之间的联系机制，采用生物素转换技术评估钙通道的S-亚硝基化。AF患者左心房组织中可见S-亚硝基化；S-亚硝基化程度与组织谷胱甘肽含量呈负相关。在暴露于亚硝基谷胱甘肽后，表达重组人心脏钙通道亚基的HEK细胞中也可检测到S-亚硝基化。S-亚硝基化可能导致AF中观察到的I(Ca,L)对谷胱甘肽敏感的减弱。
